This invention relates to a fuel system for an internal combustion engine, and even more specifically, to a fuel system in which liquid fuel, such as gasoline, is heated to a temperature sufficient to vaporize substantially all of the liquid fuel prior to its being inducted into the combustion chamber(s) of the engine for combustion thereby to result in more efficient combustion of the fuel.
Typically, a spark ignition, internal combustion engine includes an air intake system which conducts combustion air into the cylinders or combustion chambers of the engine. Liquid fuel (e.g., gasoline) is mixed with the combustion air in proper porportion either by means of a carburetor or by fuel injection. In a carburetor, the combustion air flowing into the intake system is drawn through a venturi restriction in the flow path which in turn causes the velocity air to increase and thus causes its pressure to decrease. A fuel nozzle or jet is typically located in the venturi and the sub-atmospheric pressure of the air flowing through the venturi causes the liquid fuel to be drawn into the air stream. The flow rate of the fuel is determined by metering orifices or jets in the carburetor and the velocity of the fuel flowing through the venturi. The flow rate of the air through the carburetor is typically controlled by a butterfly throttle valve downstream from the venturi which in turn is controlled by a throttle control linkage (e.g., the accelerator pedal of an automobile). With the throttle valve open, an increased amount of air may be drawn through the carburetor which in turn causes a larger pressure drop across the venturi which in turn causes a proportionately greater amount of fuel to be drawn into the air stream. Thus, the carburetor is able to maintain a substantially uniform air/fuel ratio over the entire speed range of the engine.
In many spark ignition engines utilizing fuel injection, liquid fuel is injected under pressure into the combustion air in proper relation to engine speed, load, atmospheric conditions, etc. rather than being drawn into the combustion air by a venturi effect. In certain fuel injection systems, a premeasured quantity of liquid fuel is injected into the combustion air immediately prior to the air being drawn into the respective combustion chambers of the engine.
In either carbureted or fuel injected spark ignition engines, liquid fuel is discharged into the air stream. Due to the turbulance of the air stream and due to the fact that the fuel is usually drawn into the air stream under pressure, the liquid fuel is physically broken up into small, discreet droplets. It has been long known that if liquid fuel could be vaporized (i.e., transformed from a liquid to a gas) prior to ignition within the engine, more efficient combustion of the fuel would result.
Reference may be made to such prior art U.S. Pat. Nos. 3,492,457, 3,866,587, 3,930,477, 4,053,544, 4,106,454, 4,108,953, 4,141,327, 4,153,653, and 4,157,700 which disclose various fuel heaters and vaporization systems in the same general field as the present invention. However, the prior art references differ significantly from the fuel vaporization system of the present invention.
For example, the above-noted prior art U.S. Pat. Nos. 3,492,457, 3,390,477, 4,106,454, 4,108,953 and 4,141,327 may be generally characterized as disclosing heaters disposed in the intake manifold of the engine downstream from a carburetor venturi for heating both the combustion air flowing through the cylinders and the liquid fuel entrained therein. Of course, in order to heat the liquid fuel to a temperature sufficient to vaporized fuel, the heater must heat not only the fuel but the combustion air. Thus, these prior systems required relatively large capacity heaters.
U.S. Pat. No. 3,866,587 discloses an electrical control circuit for heating automotive fuel during cold start conditions so as to insure that the liquid fuel is more ready atomized when injected into the intake system.
U.S. Pat. Nos. 4,053,544 and 4,153,653 disclose fuel induction systems which include a vacuum chamber in communication with the air induction system. A fuel vaporizer is provided in the vacuum chamber which initially is heated by an electric coil and which, after the engine comes up to temperature, is heated by means of air surrounding the fuel line which in turn has been heated by the exhaust gases of the engine. The vaporized fuel is discharged into the vacuum chamber and then is drawn into the intake manifold through a pair of rotating screens. Additionally, a vacuum feedback system is provided which controls the supply of fuel to the vaporizer.
U.S. Pat. No. 4,157,700 discloses a fuel vaporization system in which fuel is heated by means of a magnitron microwave heater.
Among the several objects and features of the present invention may be noted the provision of an improved fuel intake system for a spark ignition engine in which liquid fuel (e.g., gasoline) is heated to a temperature sufficient for substantially complete vaporization of the fuel prior to its being introduced into the combustion air flowing into the engine;
The provision of such a fuel system which results in more efficient combustion of the fuel in the engine thus providing increased efficiency (e.g., gas mileage) and decreased exhaust emissions;
The provision of such a system in which the liquid fuel is physically broken into a fine mist or spray prior to its being heated thereby to insure more complete vaporization of the liquid fuel;
The provision of such a system which will immediately and automatically terminate the flow of vaporized fuel to the engine in the event of a fire in the fuel intake system;
The provision of such a fuel vaporization system which may be used in any attitude or position of the engine; and
The provision of such a system which is feasible and economical to manufacture, which is relatively easy to maintain, and which may be readily repaired, if repair is required.
Other objects and features of this invention will be in part pointed out and in part apparent hereinafter.